All Ecological Study of Buckeye Lake. 39 



4. Nostoc society 



5. Riccia fluitans society 



I. Lemna-Spirodela society 

 Principal species 



Lemna trisnica 

 L. minor 

 Spirodela polyrhiza 



Secondary species 

 Cladophora sp. 

 Wollfia Columbiana 

 W. punctata 



This society covers the largest areas and occurs most fre- 

 quently. The surface of the larger pools and marginal lagoons 

 is characteristically covered wholly or in large part with a mat 

 of Lemna trisulca, L. minor and Spirodela polyrhiza ; below this 

 surface mat is a thick substratum, an almost pure growth of 

 Ceratophyllum demersum which is in these pools the dominant 

 and often only species of the II association. It is almost im- 

 possible to wield the oars in the thick tangle of Ceratophyllum. 

 Wollfia Columbiana is not widely distributed but occurs in sev- 

 eral marginal pools in the east side. The fronds are so minute 

 that it is seen with difficulty. 



2. Utricularia minor society 

 Principal species 



Utricularia minor 

 Secondary species 

 Riccia fluitans 

 Lemna trisulca 

 L. minor 



Spirodela polyrhiza. 

 Spirogyra sp. 

 Nostoc sp. 



